- المجال: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
A coordinate system in which the locations of points in space are expressed by reference to three planes, called coordinate planes, no two of which are parallel. The three planes intersect in three straight lines, called coordinate axes. The coordinate planes and coordinate axes intersect in a common point, called the origin. From any point P in space three straight lines may be drawn, each of which is parallel to one of the three coordinate axes; each of these lines will then intersect one (and only one) of the three coordinate planes. If A, B, C denote these points of intersection, the Cartesian coordinates P are the distances PA, PB, and PC. If the coordinate axes are mutually perpendicular, the coordinate system is rectangular; otherwise, oblique. In meteorology, the most common orientation of the x, y, z rectangular Cartesian coordinates is such that the x axis is directed toward the east, tangent to the earth's surface; the y axis toward the north, tangent to the earth's surface; and the z axis toward the local zenith, perpendicular to the earth's surface. Compare curvilinear coordinates.
Industry:Weather
A current flowing adjacent to another current but in the opposite direction.
Industry:Weather
A convenient unit of viscosity, defined as one hundredth of a poise, or 10−2 gm cm−1s−1.
Industry:Weather
A controlled airspace extending upward from a specific height above the surface of the earth in which radio contact between pilots traversing the airspace and air traffic control is required.
Industry:Weather
A condition whereby the stage, and thereby the rating curve, of a river at a point is controlled by the discharge and the shape, slope, and roughness of the channel over a considerable length.
Industry:Weather
A continuous sheet of land ice that covers a very large area and moves outward in many directions. This type of ice mass is so thick as to mask the land surface contours, in contrast to the smaller and thinner highland ice. The continental glacier of Greenland is sometimes called the Inland Ice. This term is often used to describe the great ice masses that characterized the ice ages.
Industry:Weather
A condition whereby entrainment of dry air into a cloud top causes even more entrainment, leading to the dissipation of the cloud. When the entrained air mixes with cloudy air, evaporation of the cloud drops into the mixture causes the mixture to cool. As this cool mixture sinks, it generates a turbulent circulation that can cause more entrainment, thereby continuing the process until the cloud dissipates. While there is still debate about the requirements for such a process to occur, one of the first suggestions was that this instability will occur when Δθe < Δθe critical, where Δθe is the difference of equivalent potential temperature from just above to just below cloud top, and Δθe critical is a critical value that is near zero. While the exact value of Δθe critical has yet to be determined, it depends on the buoyancy of the air (i.e., on virtual potential temperature) and on the temperature change possible due to latent heat changes when cloud droplets evaporate.
Industry:Weather
A condition in a stream where, at a certain point, the water depth passes from above critical depth to below critical depth. A change in flow conditions downstream of the point of critical depth is not readily transmitted above the control. Thus the relation between stage and discharge above the point of critical depth is fixed (or controlled) by the hydraulic characteristics of the channel at the section of critical depth. A critical depth control is usually found at a point where the channel slope steepens considerably, as above a rapids or waterfall.
Industry:Weather
A condensation nucleus formed as a result of industrial, transport, or natural combustion processes. The chemical nature of such nuclei may vary almost as much as can the nature of reactants in combustion processes, but because of the prevalence of sulfur impurities in many fuels, the process transforming sulfur dioxide (SO2) to sulfur trioxide (SO3) and thence sulfuric acid is perhaps the most important in producing combustion nuclei. Sulfuric acid is very hygroscopic and hence can serve to nucleate atmospheric condensation processes. The role of the ammonium ion (NH4+), which is formed in some combustion processes, is probably of almost equal importance to that of the sulfite (SO3−2) and sulfate (SO4−3) ions. Such nuclei may be completely or (in association with soot) partly soluble in water.
Industry:Weather
A colorless, odorless, very toxic gas; formula CO, molecular weight 28. It is an intermediate product in the oxidation or combustion of organic material. It is present in the atmosphere at varying levels but is found everywhere, a result of its widely distributed sources and fairly long lifetime. Carbon monoxide is oxidized to carbon dioxide by the hydroxyl radical (OH) and plays a part in local and regional air quality.
Industry:Weather
